Part 210 (1/2)

11. E. scirpodes, Michx. _Stems very numerous in a tuft, filiform_ (3--6' high), _flexuous and curving, mostly 6-grooved_, with acute ridges; _sheaths 3-toothed_, the bristle-pointed teeth more persistent; central air-cavity wanting.--Wooded hillsides, N. Eng. to Penn., Minn., and northward. (Eu.)

ORDER 131. FiLICES. (FERNS.)

_Leafy plants, with the leaves_ (fronds) _usually raised on a stalk or petiole_ (stipe), _rising from a_ (sometimes greatly elongated) _rootstock, separately rolled up_ (circinate) _in the bud, and bearing on the under surface or along the margin small reticulated sporangia, which at length split open and discharge the numerous minute spores.

Prothallus green, above ground, normally moncious._

SUBORDER I. Polypodiaceae. Sporangia collected in dots, lines, or variously shaped cl.u.s.ters (_sori_ or _fruit-dots_) on the back or margins of the frond or its divisions, cellular-reticulated, stalked, the stalk running into a vertical incomplete many-jointed ring, which by straightening at maturity ruptures the sporangium transversely on the inner side, discharging the spores. Fruit dots often covered (at least when young) by a membrane called the _indusium_ (or less properly the _involucre_), growing either from the back or the margin of the frond.

(Plates 16--19.)

Tribe I. POLYPODIEae. Fructification on the back of the frond, in round or roundish fruit-dots (_sori_) placed on the veins or at the ends of the veins, without indusium of any kind. Stipes articulated to the rootstock, leaving a distinct scar when separated. Veins free (not reticulated) in our species.

1. Polypodium. Sori round, in one or more rows, on each side of the midrib or of the segments of the frond.

Tribe II. GRAMMITIDEae. Sori more or less elongated, without indusium, placed on the back of the frond, usually along the veins or near their extremities. Veins free in our species.

2. Notholaena. Sori short, of few rather large sporangia, placed near the tips of the veins; under surface of the frond usually either chaffy, woolly, or powdery.

Tribe III. PTERIDEae. Fructification marginal or intramarginal, provided with a general indusium formed of the (either altered or unchanged) margin of the frond. Stipes not articulated to the rootstock. Veins free in all our species.

[*] Sporangia at the ends of the veins, on a reflexed portion of the margin of the frond.

3. Adiantum. Midrib of the pinnules marginal or none. Stipe black and polished.

[*][*] Sporangia borne on a continuous marginal vein-like receptacle, connecting the apices of the veins, and covered by a delicate whitish indusium formed of the reflexed margin.

4. Pteris. Midrib of the pinnules central. Stipe light colored.

[*][*][*] Sporangia at or near the ends of the unconnected veins, borne on the under surface of the frond; indusium various.

5. Cheilanthes. Sori minute, at the ends of the veins; indusium continuous or interrupted. Fronds mostly chaffy, woolly, or pulverulent, rarely smooth.

6. Pellaea. Sori on the upper part of the veins, distinct, or mostly forming a confluent submarginal band of sporangia. Indusium membranaceous, continuous, rarely wanting. Sterile and fertile fronds not very unlike; stipes dark colored; fronds smooth.

7. Cryptogramme. Sori roundish or elongated and extending far down the free veins, at first covered by the very broad continuous indusium, at length exposed and confluent. Sterile and fertile fronds very different; stipes light colored; fronds smooth.

Tribe IV. BLECHNEae. Sori oblong or linear, borne on a veinlet parallel to the midrib, and covered with a special usually concave or arched indusium attached to the fruiting veinlet, and opening along the inner side.

8. Woodwardia. Sori forming a chain-like row each side of the midrib or central vein. Veins reticulated.

Tribe V. ASPLENIEae. Sori more or less elongated, occupying one or both sides of oblique veins, covered by a special indusium which is attached by one side to the fertile vein, and is free on the other. Stipes not articulated.

9. Asplenium. Sori on the upper side or rarely on both sides of a veinlet. Veins free in all our species.

10. Scolopendrium. Sori linear, confluent in pairs, each pair appearing like a single sorus with a double indusium opening down the middle.

Veins free.

11. Camptosorus. Sori oblong, variously curved, or some of them in opposite pairs. Veins reticulated.

Tribe VI. ASPIDIEae. Sori round or roundish, on the back or rarely at the apex of the vein, with a special indusium, rarely naked. Stipes not articulated to the rootstock.